Changes in capillary distribution in rat fast muscles following nerve crush and reinnervation.

The recovery of muscle weight and contraction tension was measured in rat anterior tibialis muscle following unilateral crushing of the lateral popliteal nerve. Muscle twitch and tetanic tensions and muscle weight had recovered to control values within 6-8 weeks after the nerve was crushed. Capillary supply to each of the four types of muscle fibre present in the intact muscle, and within the groups of adjacent fibres of similar histochemical reaction for succinate dehydrogenase and myofibrillar actomyosin ATPase found in the reinnervated muscle, was computed by the method of Gray & Renkin (1978). Capillary area density (capillaries/mm2) within the grouped regions of the reinnervated muscle was not significantly different from the supply to the same fibre type in intact contralateral muscles. Capillary/fibre ratio for the more glycolytic fibre types (alpha W, alpha?) was lower than in intact muscle, while the values for both alpha R and beta R oxidative fibres agreed closely with control values. It seems that selective growth and loss of capillaries occurs during reinnervation, adjusting capillary supply to meet the changed metabolic demands of the individual fibres following regrouping.